This application claims the priority of French application FR/01.02280, filed Feb. 20, 2001, the entire disclosure of which is incorporated herein by reference.
1. Technical Field
The invention relates to the field of sports involving gliding over snow and, more particularly, downhill skiing. It relates more specifically to downhill skis equipped with a platform for raising the binding. It relates more particularly to a novel configuration of the zone of contact between the actual ski and the raising platform.
2. Prior Art
Downhill skis are generally equipped with a safety binding composed of a front stop and a heel piece. It has already been proposed to fit the two elements of the binding not directly onto the board for gliding, but onto a raising platform which is itself secured to the board. This raising platform makes it possible to ensure unclamping of the binding relative to the ski, i.e. to limit the influence of the stiffness of the boot sole on that of the board for gliding.
Various architectures for the raising platform have already been proposed and, in particular, that described in document EP 0 744 196, which corresponds to document U.S. Pat. No. 5,944,336.
One of the platforms described in that document has a planar central zone capable of receiving the front stop and the heel piece of the binding. This planar central zone extends laterally via two lateral portions, the lower edge of which interacts with the board for gliding. To this end, the board for gliding has, in its lateral zones, recesses inside which the lateral portions of the platform are placed. More precisely, in these lateral zones, the board for gliding has thinner zones. The raising platform thus straddles the central part of the board for gliding, resting both on the central part of the board for gliding and on the base of the recesses made in the lateral zones of the board.
A further example of a raising platform was described in document FR 2 781 166. The board for gliding described in that document has, in its lateral zones, recesses on which the lateral portions of the platform can rest. These recesses are produced above a reinforcement element which forms the side of the ski. This reinforcement element is located in line with the bead of the metal edges, and in particular makes it possible to transmit bearing forces efficiently toward said edges.
Owing to the geometry of the lateral zones of the platforms described in these documents, the bases of the recesses made in the board are totally parallel to the gliding sole plate.
The presence of the recesses on the lateral faces of the board affects the stiffness of the board and the way in which the forces are transmitted from the user""s foot toward the edges.
One of the aims of the invention is to improve the ski""s behavior by modifying the influence of these recesses.
The invention relates firstly to a raising platform for a binding for boards for gliding. In a known manner, such a platform includes a planar central zone capable of receiving the front stop and the heel piece of the binding, and two lateral portions of which the lower edge is intended for interacting with the board for gliding or for facing portions thereof.
According to the invention, this platform is noteworthy in that the lower edge of the lateral portions has, in a longitudinal plane, a non-zero gradient relative to the plane of the central zone.
In other words, the platform comes into contact with or faces the board for gliding or, more generally, interacts with the latter via zones which are not parallel to the gliding sole plate or to the topsheet of the ski, but which has a gradient.
In this way, by being displaced in a longitudinal direction, the point of contact between the platform and the board for gliding is located at a height which can vary relative to the gliding sole plate. The lateral portions of the platform, when they come into contact with the board for gliding, thus exert a force on a point of contact which is located at a distance which can vary relative to the plane receiving the front stop and the binding. This arrangement is advantageous and makes the ski behave better particularly during the transition between the phases of initiating a turn and executing the turn.
Advantageously, in practice, the lateral portions of the platform extend from either side of the boot center position.
The invention also relates to a board for gliding equipped with such a platform. In a known manner, this board includes:
a lower gliding surface composed of a gliding sole plate bordered by metal edges;
a topsheet;
lateral zones, extending on either side of the topsheet, receiving the contact of the lower edges of the lateral portions of the platform;
According to the invention, this board is noteworthy in that the lateral zones have recesses, the lower part of which includes a slope which is inclined longitudinally relative to the gliding surface of the board.
Moreover, the lower edges of the lateral portions of the platform include a complementary slope which is inclined longitudinally relative to the gliding surface of the board.
In other words, the platform according to the invention is placed on the board for gliding with its lateral portions which are inserted in complementary recesses or housings located on the board. The gradient of the lower edges of the lateral portions of the platform is identical to the gradient of the base of the recess of the board relative to the gliding surface, such that the zone in which the platform and the recesses of the board face one another extends over a great part of the recess.
The variable thickness of the board for gliding in the region of the recesses gives the board properties which improve the distribution of the forces exerted by the skier, particularly in the phases of initiating a turn and executing the turn.
This arrangement may be employed for numerous board architectures, irrespective of their internal structure and of the fact that these may be skis xe2x80x9cwith sidesxe2x80x9d or skis xe2x80x9cwith a shellxe2x80x9d.
Thus, in the case of a ski with sides, the board has lateral reinforcement elements located in line with at least one part of the bead of the metal edges. In this case, the recesses of the lateral zones form hollowed zones which are connected to said lateral reinforcement elements. In other words, the recesses of the lateral zones of the board form hollowed zones inside the lateral reinforcement elements. In these hollowed zones, the thickness of the lateral reinforcement element is less than that which it has in the rest of the ski, and it can also vary, thus forming the characteristic slope.
In a particular embodiment, the base of the recesses may have an orientation inclined toward the front and toward the bottom of the board. In other words, the thickness of the ski is less in front of the recesses than to the rear of the latter. Of course, the other orientation may also offer certain advantages. In this case, the base of the recesses has a gradient oriented toward the rear and toward the bottom of the ski.
In this latter case, the gradient of the zone of interaction between the platform and the board, particularly when it is produced actually inside the reinforcement element, moves the bearing pressure toward the front of the ski during turning and thus improves the actual execution of the turn. In other words, when the characteristic recesses are shallower on the front side of the board, the latter is relatively stiffer in the front part of the underfoot zone than in the rear part of this same underfoot zone. In the event of use of a reinforcement element, the lower height of the lateral reinforcement element is located more in the rear part of the underfoot zone. This phenomenon concentrates maximum power during edging and thus maximum gripping of the ski under the foot during initiation of a turn.
In a particular embodiment, the board for gliding may include, to the front and to the rear of the lateral portions of the platform, an additional element interposed between the lower face of the platform and the topsheet of the board. This additional element is intended for modifying the dynamic behavior of the board. This additional element may be produced either from a viscoelastic material, when it is desired to obtain certain damping properties, or may also be produced from an elastic material when it is desired to make the board more dynamic and to ensure a more rapid return to position after a bending of the board opposed by the platform.
In certain variant embodiments, the board for gliding may include a number of recesses made on the same side of the board. These recesses, numbering two or three, may have gradients oriented in the same direction or, in a preferred embodiment, in opposite directions. The platform then includes lateral portions of which the lower edges have complementary gradients.
Thus, in a particular embodiment, the board has two recesses on each side. The recess located to the front has a gradient oriented toward the bottom and toward the front. The recess located to the rear has a gradient oriented toward the top and toward the front (or, in an equivalent manner, toward the bottom and toward the rear).